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WESTERN LOWLAND GORILLA.
Term Paper ID:23814
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Essay Subject:
Evolution & phylogeny, range, habitat, survival adaptations, food, brains, population.... More...
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10 Pages / 2250 Words
5 sources, 5 Citations,
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Paper Abstract:
Evolution & phylogeny, range, habitat, survival adaptations, food, brains, population.
Paper Introduction:
Gorilla gorilla gorilla, otherwise known as the Western lowland gorilla, has not been as well studied as its ethnic relative, the eastern mountain gorilla. This paper will examine the lowland gorilla in detail, with attention to the following topics: evolution and phylogeny; range (extent, climate, and vegetation) habitat and niche, including metabolic features; physiological adoptions for survival; status of endangerment; and anatomical adoptions for survival, including population trends. In addition, three figures, mentioned in the text, will help illustrate several of the above topics.
The Western lowland gorilla's scientific name is Gorilla. It belongs to the family Pongidae, and its common name is gorilla. G. g. gorilla is a subspecies of the single species G. gorilla. The Western lowland gorilla is found in extreme
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g. Indeed, Gabon may contain as much as half the entire western population. Theirdiet varies greatly from place to place, the differences being as much"cultural" as anything else. If theWestern mountain gorilla falls above or below the norm of either of thesetwo factors, it will be particularly vulnerable to extinction. The Western lowland gorilla's scientific name is Gorilla. Gorilla gorilla gorilla, otherwise known as the Western lowlandgorilla, has not been as well studied as its ethnic relative, the easternmountain gorilla. The human stomach could notdigest the barrage of rough vegetation that gorillas in general haveadapted to by virtue of their ecological niche in the rain forest, eitherhigh or low. A complete guide to monkeys, apes, and otherprimates. In addition, the fact that the gorilla does not seem to beable to swim is another factor influencing is range. NaturalHistory. As Fleagle points out, a simplistic summary of this view is thatgorillas are overgrown chimpanzees and that pigmy chimpanzees (also knownas bonobos) are morphologically similar to immature chimpanzees; that is tosay, "the adult bonobos have a morphology that resembles the juvenilemorphology of common chimpanzees, and that adult chimpanzees have amorphology that corresponds to that of a juvenile gorilla. As Smuts writes: The least endangered of the subspecies is the Western lowland gorilla, especially in Gabon, where the human population is low, and vast tracks of forest still exist. The Western lowland gorilla,like all gorillas, is adept at handling problematic foods such as nettleswith ease. In the Eastern lowland gorilla the coloration of theskin and hair is jet black, whereas in the Western lowland gorilla the hairis more grayish or brownish, and the male's saddle of whitish hair extendsonto the thighs and grades more into the body color. For the Western lowland gorilla food is plentiful, life isleisurely, and there are few dangers except for those posed by humans. Only in the Colobinae--the leaf- eating monkeys--is the stomach large and sacculated. A simplistic summary of thisview is that each ape species mentioned above represents a different pointon the same growth curve" [figure 7.13] (2). gorilla is asubspecies of the single species G. Like chimpanzees--and ourselves--gorillas have simple stomachs,unable to neutralize plant poisons or otherwise deal with tough leaves.Thus, over much of the species' range, gorillas eat ripe fruit, rich inenergy but poor in nutrients such as protein and trace elements. Walker's mammals of the world. Evolution (genetic change in a population through time) and phylogeny(the evolutionary branching sequence) both point to the fact that gorillasand man share a common ancestor. The salivary glands, the parotid and the submandibular, are also enlarged. In any event, the Western lowlandgorilla's range is an average of 854 meters per day, throughout the year,from a locus of extreme southeastern Nigeria, southern Cameroon, extremesouthwestern Central African Republic, and so on (see earlier descriptionof territorial boundaries). Smuts contributes these demographics as well: "Within regions,population densities obviously vary according to habitat, but acrossAfrica, density normally ranges from .35 to .75 animals/km squared.Biomass ranges from .3 to .65 kg/ha" (5). The point of the above figures with regard torange is that movements within the course of a year were not random, butfollowed an established migratory pattern with respect to availability offood. In afascinating article Natural History, the author places the gorilla in itsnatural habitat, and it is apparent that manual dexterity has enabled it toadapt to a thorny situation--and why should a gorilla bother with acomplicated feeding procedure?: Most gorillas live in moist tropical forests where leaves are inedible, protected by poisonous compounds and strengthened by the indigestible, organic substance lignin; but gorillas of the Virunga Volcanoes in Rwanda and Zaire live in mountain meadows, on the densely vegetated flanks of the craters. The hypothesis that the pigmy chimpanzee is the common ancestor(prototype) of humans, chimpanzees, and gorillas is bold in light of thefact that the records available for reconstructing primate phylogeny aremeager, consisting of individuals of about two hundred living species andoccasional bony remains of several hundred extinct species drawn fromvarious parts of the world at various times during the past 65 millionyears. R. According to Shaller, the gorilla is diurnal, withnearly all activity occurring between 6 and 18 hours. Mountain gorillas eat tough, fibrous barkand roots in preference to the leaves and fruit favored by the lowlandgorillas. Marsh, Clive W. Zihlman'sevidence derives from the fact that the scant hominid fossil record and theabsence of any fossil chimpanzees or gorillas forces us to work backwardsfrom the living hominoids to reconstruct a prototype of the commonancestor. The gorillas' plant-preparation talents are no doubt dependent on theprehensile hands, "hands made more dexterous by the extensive corticalareas of the brain devoted to delicate control of finger movements" (6).The mountain gorillas' intelligence (adaptability to problematicvegetation) enables them to remain in the mountains, whereas the lowlandgorillas have no reason to leave (the food is easier to manage), and waterposes a natural barrier as mentioned previously. Byrne, Richard W. It belongsto the family Pongidae, and its common name is gorilla. A small population of G. Not only does the gorilla's ingenuity at managing nettles,thistles, and sticky/stinging leaves provide it with an abundance ofnutritional opportunities, but also the animal's stomach does a remarkablejob of processing raw foliage. Despite their differences in size, diet, and social organization, thethree living African apes "are quite similar in many aspects of cranial andskeletal anatomy and virtually identical in many biochemical assays" (2).Are their differences merely a corollary of their differences in body size,then? Primate evolution and human origins. When an area is drier, the animal may have to expandits range to accommodate more food. Liss, Inc., 1987.4. Ifthis cladogram is correct, then an ancestor for the earliest hominids mustalso be a suitable ancestor for chimpanzees and gorillas. Baltimore, MD:Johns Hopkins University Press, 1983.5. Fossey andHarcourt suggest that daily movement is usually about 4 to 1, meters... As Fleagle has pointedout, "Many authors have suggested that most of their differences are acorollary of their differences in body size. The Western lowland gorillais found in extreme southeastern Nigeria, southern Cameroon, extremesouthwestern Central African Republic, mainland Equatorial Guinea, Gabon,Congo, and the extreme western tip of Zaire, along with the Cabinda enclaveof Angola, at the mouth of the Congo River. Without deftness of movement, theWestern lowland gorilla could not perform the pinching, cupping, pulling,and stripping required to get at the edible part of a nettle clump. The animal also manages its way around thistles, wild celery,and bedstraw, all of which have either hard outer skins or tiny, stickyhooks. This is one area in which Pongidae and the human ape are farapart. There is a subspecies called the Eastern lowland gorilla (G. In general, the Western lowland gorillainhabits parts of the great forest block between Cameroon and the Congo(Zaire) River. Nowak, Ronald M. gorilla. The Westernlowland gorilla eats more bananas than his mountain counterparts, probablybecause of the superabundance of other "culturally" favored food in thehighlands. As Nowalk notes with regard to the gorilla's range, "Groupsobserved by Shaller moved from 9 to 1,8 meters per day ... The gorilla'sreluctance to wade even across shallow streams may partially explain theunusual distribution of the species (3). g. Hair color is the only genetic distinction between the two subspeciesof lowland gorilla. Primate conservation in the tropical rainforest. Zoo guides to the feeding of gorillas provide information onmetabolism--how much to feed, and how often. See figure 7.13 for an illustration. The gorilla is accustomed toeating raw and rough foods, requiring a stomach fermentation process totranspire. In the mid-196 s, Shaller estimated the entirepopulation of eastern gorillas as 5, -15, individuals. And likechimpanzees, they make up these dietary inadequacies with supplements--insects, buds, flowers, fungus, and bark. Primate adaption and evolution. Goodall determined that movements in the course of a year werenot random, but followed an established migratory pattern with respect toavailability of food. In terms of the animal's range, food appears to be the maindeterminant in overall group movement. New York, NY: Alan R. gorilla. New York, NY: Viking Press, 1983.8. As of the mid-198 s, comparatively little was known about the overallstatus of G. Not that the Western lowlandgorilla's environment is harsh by Pongidae standards, but, as has beenpreviously stated, humans could not masticate nor chemically process thegorilla's diet. g. The fact that the gorilla has made anatomical adaptations forsurvival can be seen in the hands. Marsh offers an optimal scenario for longterm genetic survival of the gorilla: "the reproductive interval should besufficiently short to replace losses rapidly and allow for expansion toavailable habitat [and] gestation length must be long enough for thedevelopment of a complex neural system to permit the behavioral complexitythat can facilitate adaptation to new or changed environments" (8). In his "Pygmy Chimpanzee as a PossiblePrototype for the Common Ancestor of Humans, Chimpanzees, and Gorillas," A.L. Smuts, Barbara B. The adults ofeach species, in this view, represent different points on the same growthcurve" (2). R. paniscus, chimpanzee andbonobo, respectively) on a list of seventeen species which can beconsidered particularly vulnerable in that they are limited indistribution, but at present abundant in a few areas, or widespread butthreatened in many places (8). A survey of Marsh's Primate Conservation in the Tropical Rain Forestplaces Gorilla (along with Pan troglodytes and P. Unfortunately, as of the early198 s, this prediction could not be tested because of the very few data onmetabolic rates for primate species. Gorillas are entirely vegetarian in their natural habitat. "Jones andSabater Pi (1971) considered the western lowland gorilla to be decliningbecause of habitat destruction and killing by people for food and allegedlyto protect crops. Folivorous primates (gorillas) tendto have relatively small brains and they have relatively low metabolicrates. Goodall and Groves stated that during the wet season of April throughJune in eastern Zaire groups moved an average of 596 meters per day, butthat in the dry months of July through August, they covered an average of1,24 meters per day" (3). A. New York,NY: Aldine de Gruyter, 1987.2. Martin and Armstrong's work with allometry of brain size have leadthem to the prediction that subfamilies with high metabolic rates (humans)will have relatively large brains (5). The ruminant-like digestive system, in which large quantities of mature leaves are processed by fermentation, can presumably be correlated with a predominantly folivorous diet (4). The bonobo, chimpanzee, and gorilla are allthree in the current IUCN Mammal Red Data Book as "Threatened Species ofAfrican Forest Primate" (8). Even the leaves eaten by the Western lowland gorilla would be morethan the tender human stomach could withstand. Pigmy chimpanzees are more "generalized" in body size, bodybuild and sexual dimorphism than the common species, and may provide a goodprototype for studying the derivation of the earliest hominids and Africanapes. However, the Westernlowland gorilla has been better off. 1 4 (1 ):13; 1995.1. Not all of the tropical rain forest vegetation--like the nettle--is easy to handle, but the gorilla's intelligence allows it to follow acomplex sequence of actions to remove or neutralize all of the nettle'sdefenses. The gorilla is vulnerable inmost parts of its range, as Shaller (1963) has pointed out (see citation5), especially in East Africa, where populations are often split into tiny,isolated pockets surrounded by human habitation. The jaws and teeth of mountain gorillas are particularlymassive (7), perhaps a natural adaptation to the rougher foliage. The natural history of the primates.Cambridge, MA: MIT Press, 1986.3. Kavanagh, Michael. Ciochon, Russell L. Figure 1 gives a molecularcladogram showing genetic relationships of the ape and human lineages. Estimates of gorilla numbers in West Africa are rough guesses everywhere except in Gabon, where a recent census indicated a population of about 35, gorillas (5). Afterawakening, the animals feed intensively for a while, then rest from about1 to 14 hours, and then travel and feed until bedding down for thenight. Primate societies. Marsh further makes the point that long-livedspecies such as Pan troglodytes and Gorilla have low productivity rates andhigh parental investment in each offspring (a gorilla female produces onlyone offspring every four years). In summation, the lowland gorilla's range is determined by itsrelative inability to swim, its affinity for avoiding other groups, and itsseeking out of food. g.graueri) which is separated by about 1, kilometers from the Westernlowland gorilla. San Diego, CA:Academic Press, 1988.7. Literature Cited6. gorilla that once may haveexisted in the Bondo district of north-central Zaire has not been reportedsince 19 8 (Goodall and groves, 1977)" (3). Napier, J. This paper will examine the lowland gorilla in detail,with attention to the following topics: evolution and phylogeny; range(extent, climate, and vegetation) habitat and niche, including metabolicfeatures; physiological adoptions for survival; status of endangerment; andanatomical adoptions for survival, including population trends. Zihlman points to biochemical as well as anatomical similarities betweenhumans and their primate relatives when he notes, "Phylogeneticrelationships have previously been determined mainly by anatomicalsimilarities, but now, biochemical similarities provide independentcriteria for evolutionary relationships" (1). Some researchers such as Fosseyhave maintained that gorillas go our of their way to avoid contact withanother group. G. The implication for long term genetic survival is that the lesserthe brain size, the greater is the evolutionary necessity that the animalphysically adapt to a harsher environment. The fact that Westernlowland gorillas have relatively broad faces with smaller jaws and teeththan their eastern, mountain relatives may have significance with regard toadaptation. In terms of physiological and anatomical adaptations for survival, itcan be said that despite their differences in size, diet, and socialorganization (pertaining to range and habitat), the three living Africanapes (Gorilla, Pan troglodytes, and Pan paniscus) are quite similar in manyaspects of cranial and skeletal anatomy, and virtually identical in manybiochemical assays [see figures 3.12 and 7.13]. An isolated population of thissubspecies may also have existed in the Bondo district of north-centralZaire. The "way of life" the Western mountain gorilla pursues within itshabitat, or its status or position within the ecosystem, or niche, isuppermost. Inaddition, three figures, mentioned in the text, will help illustrateseveral of the above topics. Chicago, IL:University of Chicago Press, 1987----------------------- 9 With regard to genetic survivorship and population trends, the futurelooks good for the Western lowland gorilla. G. Napier's The Natural History of the Primates describesthe digestive system of the gorilla in detail: The digestive tract does not show much in the way of specialization [the animal has a simple stomach]. Apassage from J. Here, many leaves are edible, but fruit is scare [the Western lowland gorillas get the bananas!] (6). The smart gorilla's recipe book. Fleagle, John G. Some plants--lemonwood, pepper plant, bambooand the stinging nettle Urera--are eaten wherever they occur.
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